Is this allowed now?
or would it only go through if the landing page had user age relevant content?
It's 50/50.
Facebook at one point made it clear you cannot call out any demographics in the ads, but ads slide by all the time.
jroes just posted how his campaign calling out the age went through. With approvals its not always 100%, it's up the the reviewers and a lot of the reviewers don't have a full grip of whats going on. So if it's worth pursuing to you, then keep pushing ads because eventually they will slide through.